From the points of structure in the central ridge, now enumerated,--namely,
from the convergence towards it of the beds of the upper series,--from the
lavas there becoming highly cellular,--from the flat ledge, extending along
its inner and precipitous side, like that within some still active
craters,--from the parapet-like wall on its summit,--and lastly, from its
peculiar curvature, unlike that of any common line of elevation, I cannot
doubt that this curved ridge forms the last remnant of a great crater. In
endeavouring, however, to trace its former outline, one is soon baffled;
its western extremity gradually slopes down, and, branching into other
ridges, extends to the sea-coast; the eastern end is more curved, but it is
only a little better defined. Some appearances lead me to suppose that the
southern wall of the crater joined the present ridge near Nest Lodge; in
this case the crater must have been nearly three miles long, and about a
mile and a half in breadth. Had the denudation of the ridge and the
decomposition of its constituent rocks proceeded a few steps further, and
had this ridge, like several other parts of the island, been broken up by
great dikes and masses of injected matter, we should in vain have
endeavoured to discover its true nature. Even now we have seen that at
Flagstaff Hill the lower extremity and most distant portion of one sheet of
the erupted matter has been upheaved to as great a height as the crater
down which it flowed, and probably even to a greater height. It is
interesting thus to trace the steps by which the structure of a volcanic
district becomes obscured, and finally obliterated: so near to this last
stage is St. Helena, that I believe no one has hitherto suspected that the
central ridge or axis of the island is the last wreck of the crater, whence
the most modern volcanic streams were poured forth.

The great hollow space or valley southward of the central curved ridge,
across which the half of the crater must once have extended, is formed of
bare, water-worn hillocks and ridges of red, yellow, and brown rocks,
mingled together in chaos-like confusion, interlaced by dikes, and without
any regular stratification. The chief part consists of red decomposing
scoriae, associated with various kinds of tuff and yellow argillaceous
beds, full of broken crystals, those of augite being particularly large.
Here and there masses of highly cellular and amygdaloidal lavas protrude.
From one of the ridges in the midst of the valley, a conical precipitous
hill, called Lot, boldly stands up, and forms a most singular and
conspicuous object. It is composed of phonolite, divided in one part into
great curved laminae, in another, into angular concretionary balls, and in
a third part into outwardly radiating columns. At its base the strata of
lava, tuff, and scoriae, dip away on all sides (Abich in his "Views of
Vesuvius" plate 6 has shown the manner in which beds, under nearly similar
circumstances, are tilted up. The upper beds are more turned up than the
lower; and he accounts for this, by showing that the lava insinuates itself
horizontally between the lower beds.); the uncovered portion is 197 feet in
height (This height is given by Mr. Seale in his Geognosy of the island.
The height of the summit above the level of the sea is said to be 1,444
feet.), and its horizontal section gives an oval figure. The phonolite is
of a greenish-grey colour, and is full of minute acicular crystals of
feldspar; in most parts it has a conchoidal fracture, and is sonorous, yet
it is crenulated with minute air-cavities. In a S.W. direction from Lot,
there are some other remarkable columnar pinnacles, but of a less regular
shape, namely, Lot's Wife, and the Asses' Ears, composed of allied kinds of
rock. From their flattened shape, and their relative position to each
other, they are evidently connected on the same line of fissure. It is,
moreover, remarkable that this same N.E. and S.W. line, joining Lot and
Lot's Wife, if prolonged would intersect Flagstaff Hill, which, as before
stated, is crossed by numerous dikes running in this direction, and which
has a disturbed structure, rendering it probable that a great body of once
fluid rock lies injected beneath it.